ABSTRACT
Purpose: Current strategies implementing drug-eluting polymer stent coatings fail to fully address the lasting effects of endothelial suppression which ultimately result in delayed reendothelialization and thrombogenic complications. The present study investigates the in vitro hemocompatibility of all-trans retinoic acid loaded poly (1,8-octanediol-co-citrate) coatings (AtRA-POC coatings) for advanced intravascular stent technology. The ability of these materials in supporting endothelial restoration via migration and proliferation while inhibiting smooth muscle cell growth is also explored. Methods: Using in vitro models, the hemocompatibility of AtRA-loaded POC-coated cobalt chromium (CoCr) vascular stents was evaluated in terms of platelet and inflammatory activity. Platelet activity was quantified by platelet adhesion and platelet activation, further supported by SEM visualization. Inflammatory activity was quantified by the production of proinflammatory cytokines by THP1 monocytes. Lastly, in vitro wound healing and an 5-Ethynyl-2'deoxyuridine (EdU) and pico green DNA assays were used in quantitating endothelial and smooth muscle cell migration and proliferation. Results: Experimental examinations of platelet adhesion and activation demonstrate significant reductions in the platelet response to POC coated AtRA loaded stents when compared to bare CoCr stents. Such findings reveal AtRA-POC coatings to have significantly improved hemocompatibility compared to that of bare metal stents and at least as good as POC alone. Similarly, in reference to LPS-stimulated controls, Human monocyte-like THP1 cells in culture with AtRA-POC-CoCr stents for 24 hours showed reduced detection of proinflammatory cytokines, comparable to that of bare CoCr and untreated controls. This result supports AtRA-POC coatings as possessing limited immunological potential. Observations from in vitro endothelial and smooth muscle cell investigations demonstrate the ability of the drug AtRA to allow cell processes involved in restoration of the endothelium while inhibiting smooth muscle cell processes. Conclusion: This study demonstrates AtRA loaded POC coatings are hemocompatible, noninflammatory, and provide a promising strategy in enhancing vascular stent techniques and clinical integration. Possessing hemocompatibility and immunological compatibility that is at least as good as bare metal stents as clinical standards support the use of AtRA-POC coatings for vascular applications. Additionally, selectively reducing smooth muscle cell proliferation while supporting endothelial cell proliferation and migration further demonstrates the potential of these materials in significantly improving the state of vascular stent technology in the area of stent thrombosis and neointimal hyperplasia.
